In the past number of years there has been a continuously increasing surge of interest in winter sports activities, particularly those activities which need a snow base for operation, e.g., skiing, snowmobiling, snowshoeing and the like. Unfortunately, in many areas of the world the natural snow fall is not predictable nor sufficient to assure continuous operation during the season of sports areas and resorts having facilities for such winter sports.
In more recent years continuity of operation and a good snow base has been gained by the use of snow-making machines and apparatus. With such equipment snow-based winter sports activities have been continuously operated during the winter season and extended to geographical areas of the United States; for example, as far south as North Carolina, Virginia and Tennessee even though there is usually not sufficient natural snow in these areas to permit such sports on a regular basis during the season.
With snow making equipment it is essential only that there be an ambient temperature below about 32.degree. F. (0.degree. C.) for a period sufficient to permit snow making to continue until an adequate depth of snow is deposited on the area, terrain or slope desired to be covered. In areas of North Carolina and Tennessee, for example, during a typical winter sports season there may be only 25 days with good conditions for making snow. Farther north in Ohio 30 to 40 days snow making operation ordinarily can be expected and in Michigan 50 days or more are not uncommon. Therefore, it is important for effective operation that large volumes of snow be made rapidly during those periods when conditions are right for mechanical snow making.
Snow making apparatus and machines which have gained widespread commercial acceptance to date have varied both in the type of construction and correspondingly in their method of operation to generate snow. The term "snow" as used herein will refer to the crystallized product resulting from the crystallization of finely divided droplets of a water spray which are deposited at a distance remote from the water droplet generating site. Representative of such apparatus are those which in operation provide a stream, or multiple streams or jets of water, which impinge on rotating fan blades and are atomized into fine droplets as these are driven off the trailing edge of each blade.
Other examples of snow making machines are those which operate by mixing a stream, or multiple streams or jets of water, with compressed air to generate finely divided water droplets, transporting the droplets away from the site of their formation by force of the compressed air being exploded through an orifice. Other methods and apparatus use a fan in combination with compressed air guns. This fan or a second blower operating at ambient pressure and/or a combination of these, effect at least partial crystallization of the water droplets into snow during such transporting.
Illustrative of such apparatus is that disclosed by Pierce in U.S. Pat. No. 2,676,471. This machine mixes compressed air with water within a spray nozzle to effect particle formation of the water along with a cooling of the water which results from the adiabatic expansion of the compressed air. In commercial practice it has been found that the Pierce machine is highly susceptible to nozzle freezing. Additionally, excluding wind factors, this apparatus depends on the force of the compressed air and water themselves to move the freezing water particles beyond the immediate area of the nozzle.
Eustis in U.S. Pat. No. 3,703,991 utilizes a large fan to move particles away from a spray nozzle, but also provides additionally a system wherein compressed air and water are mixed within a first seeding nozzle as taught earlier by Pierce and water is added to the fan moved air by a second exterior nozzle. The seeding nozzles are disposed within the protective cowling of the fan; this can lead to frozen nozzles and increased mechanical difficulties in cleaning and repair. In commercial operations this apparatus has been shown to convert as much as 200 to 250 gallons of water per minute into snow under optimum conditions.
Hanson in U.S. Pat. No. 2,968,164 discloses a different type of snow making apparatus that has become commercially available. This machine includes a high powered fan for providing a substantially unidirectional high volume of air at substantially atmospheric pressure and in combination therewith an independent water spray providing means downstream from the fan. This water spray means is designed and positioned to provide a water spray which is injected into the high volume air movement from the fan at a rate and in a quantity sufficient to achieve crystallization of a substantial amount of the spray droplets and deposition of these as snow. This machine has the advantage that it operates without requiring the use of compressed air although compressed air can and often is used for nucleation. Other nucleation methods may also be used.
Ericson et al. in U.S. Pat. No. 3,610,527 have taught another modification of the apparatus of U.S. Pat. No. 2,968,164 whereby with an 18 or 20 inch fan blade from about 3 to about 140 gallons of water per minute can be converted into snow depending on the rate of rotation of the fan propeller, ambient temperature and relative humidity, and the temperature of the feed water.
Hanson in U.S. Pat. No. 4,004,732 teaches an improvement in machines for making artificial snow of the type in which during operation a water spray is directed into a high volume unidirectional mechanical movement of air, such as generated by a fan, at substantially atmospheric pressure to effect crystallization of the droplets of water in the spray and subsequent deposition of the resultant crystals (hereinafter referred to as "snow") at a position remote from the snow-making machine as snow by regularly redirecting the direction of the discharge end of the snow making apparatus during operation and to a new and useful method for efficiently producing such snow.